The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Intramolecular pyrylium ylide-alkene cyclizations provide control of the absolute stereochemistry at the crucial C-19 angular methyl group, and leads to bicyclo[5.4.0 3,8 ]undecenones that contain the structural elements of the B/C rings of the taxanes.
The bicyclo[5.4.0]undecenones 5, 6 and 7 are converted through a four step sequence involving activation, gem-methylcyclopropanation and reductive cleavage into the B/C rings of the taxanes, 18 and 19. The A-ring has been attached to the B/C ring system by cyclization of the sulfone-ester 28 to give 29, and also at a higher oxidation level; 33 gives 34. The same type of anionic cyclization is successful...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.